The present invention relates to the manufacture of yarns and fabrics and in particular relates to an improved modified polyester composition that is particularly useful for forming blended yarns from polyester and cotton.
Blended fabrics formed of polyester and cotton have found wide acceptance for fabrics, particularly for clothing. Generally speaking, a xe2x80x9cblendedxe2x80x9d fabric of polyester and cotton is formed by spinning a blended yarn from cotton fibers and polyester staple fibers. The blended yarns are then woven or knitted into the appropriate fabrics. Each of these materials brings certain advantages and disadvantages to a fabric. Cotton is, of course, formed almost entirely of pure cellulose with a typical length of about one inch, but with variations in length from about a half and inch to over two inches. Mature cotton fibers are characterized by their convolutions so that under a microscope, cotton appears as a twisted ribbon with thickened edges. Cotton is light in weight, absorbs moisture quickly and easily, and has a generally favorable texture (xe2x80x9chandxe2x80x9d) when woven into fabrics. Cotton lacks, however, certain strength characteristics and elastic memory, and thus garments formed entirely of cotton require regular laundering, pressing, and in many cases starching, between wearings by the ordinary user.
Polyester is strong, light in weight, and has excellent plastic memory characteristics. Polyester is crease-resistant, quick-drying, retains its shape in garments, is abrasion-resistant, and requires minimum care. Because of its synthetic nature, however, polyester has a generally unacceptable appearance (at least for most garment purposes) when initially formed as a filament. Accordingly, polyester filaments require texturizing in some fashion to produce acceptable characteristics of appearance, hand, and comfort in yarns and fabrics.
Accordingly, blends of cotton and polyester have found wide-ranging acceptance because of their combination of the desirable characteristics of cotton with those of polyester.
The characteristic advantages of polyester are such, however, that efforts continue to develop polyester filament, yarns and fabrics that more closely resemble those of cotton, silk, rayon, or other natural fibers. The use of polyester microfibers is one example of this, with the filaments being of such small diameter that they offer exceptionally good esthetics and hand, while retaining all of the benefits of polyester.
A number of chemical modifications have been carried out on polyester to attempt to obtain the desired properties, but such treatments can produce unwanted or unexpected characteristics in the modified polyester. For example, polyethylene glycol can enhance certain polyester properties such as dye uptake, but can decrease other properties, particularly the melt phase characteristics of the polymer, that make it quite difficult to form into acceptable filaments on a continuous commercial basis. In this regard, it will be understood that polyester filament is made in significantly large amounts around the world, and that if modified polyesters are to gain commercial acceptance, they must be essentially compatible with commercial techniques for melt-spinning, texturing, yarn spinning and fabric forming techniques; i.e., weaving and knitting.
Accordingly, a need continues to exist for enhanced polyester compositions that have properties as close as possible to those of cotton and other natural fibers while retaining the advantages of polyester.
Accordingly, it is an object of the present invention to provide a polyester composition that has certain properties substantially similar to those of cotton, while retaining the favorable properties of polyester.
The invention meets this object with a polyester composition comprising polyethylene terephthalate, polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a filament made from the composition to a level substantially similar to the properties of cotton, but less than the amount that would reduce the favorable elastic memory properties of the polyester composition, and a branching agent in amount that raises the melt viscosity of the polyester composition to a level that permits filament manufacture under substantially normal spinning conditions.
In another aspect, the invention comprises polyester filament formed from the composition.
In yet another aspect, the invention comprises yarns formed either entirely of polyester or of polyester and cotton blends.
In yet another aspect, the invention comprises woven, nonwoven or knitted fabrics formed from the polyester or blended yarns according to the present invention.
The foregoing and other objects and advantages of the invention and the manner in which the same are accomplished will become clearer based on the following detailed description taken in conjunction with the accompanying drawings in which: